help with Vibration Please
1969 Pontiac tempest that PO installed a 1971 vintage 400 and THM350.
I get a vibration/shake at 45MPH which goes away above or below that number.
I currently have the driveshaft out and the car on jackstands. If I run the car in drive, I can feel the shake at 45 displayed on the speedometer. If I put it in Low ear, at about 25. If it is in park, I can feel it at a certain engine vibration. As I increase rpms it is smooth
I thought about flywheel, but what I read was that if it was flywheel, there would be vibrations at all speeds getting worse when rpms increase.
Could this be a transmission problem? any ideas what I should look for/check.
Also, I checked motor mounts and transmission mount and they area all good
Last edited by ajluzi1957; 08-18-2017 at 09:53 AM.
Reason: update with additional information